Norepinephrine release in the cerebellum contributes to aversive learning

The modulation of dopamine release from midbrain projections to the striatum has long been demonstrated in reward-based learning, but the synaptic basis of aversive learning is far less characterized. The cerebellum receives axonal projections from the locus coeruleus, and norepinephrine release is implicated in states of arousal and stress, but whether aversive learning relies on plastic changes in norepinephrine release in the cerebellum is unknown. Here we report that in mice, norepinephrine is released in the cerebellum following an unpredicted noxious event (a foot-shock) and that this norepinephrine release is potentiated powerfully with fear acquisition as animals learn that a previously neutral stimulus (tone) predicts the aversive event. Importantly, both chemogenetic and optogenetic inhibition of the locus coeruleus-cerebellum pathway block fear memory without impairing motor function. Thus, norepinephrine release in the cerebellum is modulated by experience and underlies aversive learning.

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All studies must disclose on these points even when the disclosure is negative. No human data was used in this study.
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No human data was used in this study.
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No human data was used in this study.
No statistical methods were used to predetermine sample sizes for our experiments, but our sample sizes were based on prior literature demonstrating significance. Sample sizes for GrabNE fiber photometry experiments well exceeded those reported in previous publications in mouse (Feng et al. 2019 Note that full information on on the approval of of the study protocol must also be be provided in in the manuscript. All mice in in this study were on on a C57BL/6J background, typically group housed with littermates of of the same sex, and provided access to to food and water ad ad libitum. Mice were kept on on a reverse light/dark cycle (lights off at at 7:00, lights on on at at 15:00) and the behavioural tests were conducted during the dark phase. Adult male and female mice > 8 weeks of of age were used for all experiments. Experimental groups contained equal numbers of of male and female mice. TH-IRES-Cre+/! mouse line was obtained from Jackson Laboratory (Bar Harbor, ME, USA) and maintained by by backcrossing to to C57/B6J mice.
No No wild animals were used in in this study.
Source data, disaggregated by by sex, are provided with this manuscript. Experimental groups contained both male and female mice > 8 weeks of of age. Since the conditioned fear response is is not significant different between untreated males and females (see the Source data file), the sex was not considered in in the study design and analysis. TH-IRES-Cre+/! mouse line was obtained from Jackson Laboratory (Bar Harbor, ME, USA) and maintained by by backcrossing to to C57/B6J mice. The study included Th-Cre mice (four males and two females) injected with AAV5-synP-DIO-eGFP-WPRE-hGH virus, seven C57BL/6J mice (four females and three males) for the FFN270 experiment, twenty-four mice C57BL/6J mice (eighteen females and six males) injected with AAV9-GRABNE, fifteen Th-Cre mice injected with DREADD hM4D(Gi)-mCherry (seven females and eight males) vs vs 11 11 Th-Cre mice (three females and eight males) injected with the control YFP virus for the chemogenetic inhibition of of LC LC axons in in the CB CB during conditioning, ten Th-Cre mice (six females and four males) injected with Arch3-YFP virus vs vs 3 Th-Cre mice (two females and one male) injected with the control YFP virus for the optogenetic inhibition of of LC LC axons in in the CB CB during conditioning, seven Th-Cre mice injected with Arch3-YFP virus for the optogenetic inhibition of of LC LC axons in in the CB CB during recall.
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All experimental procedures were approved by by the Columbia University Institutional Animal Care and Use Committee (IACUC).